Center gauge



Sept. 29, 1942.

c. w. DURHAM I CENTER GAUGE Filed April 24, 1941 Attorney Patented Sept. 29, 1942 UNETE S'EA'EES F'EEisl'i @FFICE.

5 Claims.

This invention relates to drafting tools, and more particularly the invention has reference to a device for use in determining or finding the centers of circles and of round work.

Further it is an object of the invention to provide a device of this character which is extremely simple in construction so as to be cheaply manufactured and retailed for a nominal price.

It is also an object of the invention to provide a device of this character whereby through the medium of a single instrument the center of a circle or round work can be quickly and easily determined.

The invention, together with its objects and advantages will be best understood from a study of the following description taken in connection with the accompanying drawing, wherein Figure 1 is a plan view of a center gauge embodying the features of the present invention,

Figure 2 is an edge elevational view thereof,

Figure 3 is a detail sectional view taken substantially on the line 33 of Figure l, and

Figure 4 is a plan view of the gauge illustrating the manner of using the same.

Referring more in detail to the drawing it will be seen that the improved center gauge, in accordance with the present invention, is formed from a single piece of material, preferably some transparent ductile material as pyralin, cut, shaped and dimensioned to provide an oblong straight-edge 5 from one longitudinal edge of which extends an integral arm 6 that tapers, as it proceeds from the edge of the straight-edge 5 to a terminal end I; the arm or extension 6 having a relatively short leading concave edge 8 extending inwardly from the end I of the arm to the point of merger with the straight .edge 5 and a relatively longer convex edge '9 that extends from the point I to the point of merger with the straight edge 5; and a second arm or extension formed integrally with and extending from the opposite longitudinal edge of the straight edge and terminating in a terminus II that is coextensive with the terminus l.

The arm or extension H3 is provided with a relatively short concave edge l2 and a relatively longer convex edge [3; it being noted that preferably the terminus ll of the arm or extension I 0 is closer to the straight edge 5 than is the terminus of the arm or extension 6.

scribed, or otherwise formed on the surfaces of the extensions or arms 6 and ID are diagonal lines M that merge at one end as at I5 so that the angle l5 between the lines lfll4 is in direct alignment with the longitudinal edge l6 of the straight edge 5.

As shown in Figure 4 the tool may be used to advantage for determining the centers of circles, and when determining the center of a relatively large circle such as fragmentarily shown by phantom lines in Figure 4 and indicated by the reference numeral ll, the points 1 and H are positioned against the periphery of the circle or work ll exteriorly of the circle and a line then drawn along the edge 15 of the straight edge 5.

This operation is repeated at several points throughout the periphery of the circle I1, and as obvious, the point where the lines drawn along the edge E6 of the straight edge 5 intersects will indicate, accurately, the center of the circle.

In substantially the same manner the tool may be used for finding the center of a circle by placing the points I and H against the periphery of the circle within the confines of the circle as shown in Figure 4, and wherein the second referred to circle is fragmentarily shown by phantom lines and indicated by the reference numeral l8.

Also, as shown in Figure 4, the tool may be used to advantage in finding the center of a relatively small circle. In that instance the tool is positioned so that the lines 14 touch the periphery of the circle, shown by phantom lines in Figgure 4 and indicated by the reference numeral l9, and when so positioned a line is then drawn along the edge E6 of the straight edge 5. This procedure is followed at several additional points on the circle l9 and obviously, the lines drawn along the edge It, at the point of intersection of such lines, serve to indicate the center of the circle l9.

It will also be appreciated that the tool may be used to advantage for erecting perpendicular lines to convex and concave contours.

It is thought that the manner of use, and the many advantages of a tool center gauge embodying the features of the present invention will be had by those skilled in the art without further detailed description.

It is also to be understood that while I have herein illustrated and described the preferred embodiment of the invention, changes may be made therein without departing from the spirit of the invention by those skilled in the art to which this invention relates.

Having thus described the invention, what is claimed as new is 1. A tool for finding centers of circles and round work, and for erecting perpendicular lines to convex and concave contours, formed from a single blank of sheet material cut, shaped and dimensioned to provide a straight edge having integral arms extending from opposite ,edges thereof, said arms being curved and extended in the direction of length of the straight edge, and respectively terminating at points laterally spaced equidistantly from one longitudinal edge of the straight edge; said arms terminating in the plane of an imaginary line drawn at right angles transversely through the straight edge.

2. A tool for finding the centers of circles and round work, and for erecting perpendicular lines to convex and concave contours, formed from a single blank of sheet material cut, shaped and dimensioned to provide a straight edge having integral arms extending from opposite edges thereof, said arms being curved and extended in the direction of length of the straight edge, and respectively terminating at points laterally spaced equidistantly from one longitudinal edge of the straight edge; said arms terminating in the plane of an imaginary line drawn at right angles transversely through the straight edge; said tool having diagonal lines formed on the surfaces of said arms, said lines merging together at a point substantially in alignment with said one longitudinal edge of said straight edge.

3. A tool for finding the centers of circles and round work, and for erecting perpendicular lines to convex and concave contours, formed from a single blank of sheet material cut, shaped and dimensioned to provide a straight edge having integral arms extending from opposite edges thereof and intermediate the ends of the straight edge, said arms being curved and extended in the direction of length of the straight edge, and respectively terminating at points laterally spaced equidistantly from one longitudinal edge of the straight edge; said arms terminating in the plane of an imaginary line drawn at right angles transversely through the straight edge; said tool having scribed thereon in the region of said arms a substantial V with the sides of the V at a 90 angle with respect to each other and merging at a point substantially in alignment with said one longitudinal edge of said straight edge.

4. A tool for finding centers of circles and round work and for erecting perpendicular lines to convex and concave contours, and formed from a single sheet of transparent material having plane front and rear surfaces, cut, shaped and dimensioned to provide a straight edge having integral arms extending from opposite edges thereof, said arms being curved and extended in the direction of length of the straight edge and respectively terminating at points laterally spaced equidistantly from one longitudinal edge of the straight edge, said arms terminating in the plane of an imaginary line drawn at right angles transversely through the straight edge and said arms having lines displayed thereon at a angle with respect to each other merging at a point substantially in alignment with said one longitudinal edge of the straight edge and in vision at either side of the tool.

5. A tool for finding centers of circles and round Work and for erecting perpendicular lines to convex and concave contours, and formed from a single sheet of transparent material having plane front and rear surfaces, cut, shaped and dimensioned to provide a straight edge having integral arms extending from opposite edges thereof, said arms being curved and extended in the direction of length of the straight edge and respectively terminating at points laterally spaced equidistantly from one longitudinal edge of the straight edge, said arms terminating in the plane of an imaginary line drawn at right angles transversely through the straight edge and said arms having lines displayed thereon at a 90 angle with respect to each other merging at a point substantially in alignment with said one longitudinal edge of the straight edge and in vision at either side of the tool, and said arms further being of gradually increased width toward the straight edge.

CORBIN W. DURHAM. 

